1. Field of the Invention
The present invention relates to an endoscope in which a structure of a distal end portion of an insertion portion is improved.
2. Description of the Related Art
Insertion apparatuses having an elongated insertion portion which is inserted into a subject are widely used. In some insertion apparatuses, a bending portion is provided on a distal end side of the insertion portion. As an example of the insertion apparatuses, there is an endoscope with which observation and the like can be performed. As shown in FIG. 1, an elongated insertion portion 1 of the endoscope is configured with a distal end portion 2, a bending portion 3, and, for example, a flexible tube portion (not shown) having flexibility arranged from a distal end side in that order and connected to the insertion portion 1.
On a distal end face of the insertion portion 1, an observation window 4 constituting an observation optical system, for example, a pair of illuminating windows 5 constituting an illumination optical system, a distal end opening 6 and the like are provided. Further, some insertion portions are provided with a cleaning nozzle or the like for washing away blood, waste, oil or the like adhering to a surface of the observation window 4 and the like, on the distal end face.
The bending portion 3 is configured having mainly a set of bending pieces, a mesh tube and a bending rubber. The set of bending pieces is configured with a plurality of bending pieces connected so as to bend, for example, in two directions of upward and downward or four directions of upward, downward, right and left.
For example, Japanese Patent Application Laid-Open Publication No. 07-194518 shows an endoscope in which a bending shape of the bending portion is improved so as to facilitate observation and treatment. In the endoscope, a cylindrical body which covers a nozzle, a light guide and an image guide, and a most distal end bending piece are fixed to a rigid distal end component member with fixing screws.
As shown in FIG. 2, an observation optical system hole 8, a treatment instrument insertion hole 9, an illumination optical system hole and an air/water feeding hole which are not shown, and the like are formed in a distal end rigid member 7 constituting the distal end portion 2. An image pickup unit 10 is provided in the observation optical system hole 8.
The image pickup unit 10 is fixed in the observation optical system hole 8, for example, with adhesion; a channel connecting tube 15 is fixed in the treatment instrument insertion hole 9, for example, with adhesion; the light guide is fixed in the illumination optical system hole, for example, with adhesion; and a connecting tube for air/water feeding is fixed in the air/water feeding hole, for example, with adhesion.
The image pickup unit 10 is configured having an objective optical system 13 with a plurality of optical lenses 12 arranged in a lens frame 11, and an image pickup apparatus (not shown) provided with an image pickup device arranged at an image forming position of the objective optical system 13. A proximal end portion of the channel connecting tube 15 projects from a proximal end of the distal end rigid member 7, and a distal end portion of a channel tube 16 is integrally fixed to the proximal end portion. An air feeding tube (not shown) and a water feeding tube (not shown) are integrally fixed to a proximal end portion of the connecting tube for air/water feeding which projects from the proximal end of the distal end rigid member 7.
On an outer circumferential face side of the distal end rigid member 7, a distal end cover 17, a bending rubber 18, and a distal end bending piece 19 are arranged. A flange 7f is provided at a predetermined position of an outer circumference of the distal end rigid member 7. A distal end face of the distal end bending piece 19 is positioned and arranged in contact with a rising surface on a distal end side of the flange 7f. The distal end bending piece 19 is integrally and firmly fixed to the distal end rigid member 7 without backlash by two fixing screws 20 while stress of abutting against the rising surface being generated.
The distal end cover 17 is in a cylindrical shape, and its inner circumferential face is arranged on the outer circumferential face of the distal end rigid member 7. A proximal end face of the distal end cover 17 is arranged at a predetermined position on a more distal end side than the flange 7f. A distal end portion of the bending rubber 18 is arranged on the outer circumferential face of the distal end rigid member 7. A distal end face of the bending rubber 18 is in contact with the proximal end face of the distal end cover 17 arranged on the more distal end side than the flange 7f and integrally and firmly fixed by spool adhesion.
In recent years, high functionality of an endoscope, that is, improvement of observation performance due to increase in the number of pixels, improvement of treatment due to increase in size of a channel tube, addition of a function of cleaning a patient's lesion portion, addition of an enlargement function and the like have been realized. Therefore, in order to expand internal space in the distal end rigid member while realizing a shorter diameter of the insertion portion, the number of screw threads is reduced as far as possible, for example, is set to three, and thickness of a screw head is machined thin to fix a distal end bending piece to the distal end rigid member.